Aluminoxanes, for example, those of the general formula --(O--AIR).sub.n --, where R is an alkyl group, such as methyl, have received considerable attention in recent years due to their ability to form active olefin polymerization catalysts when combined with Group IV metallocenes. Among these, the most important aluminoxane is methylaluminoxane (R=methyl) since it produces the highest activity catalysts. Methylaluminoxane, however, is expensive since its synthesis requires the use of a rather expensive trimethylaluminum reagent. Furthermore, trimethylaluminum is very air- and moisture-sensitive and such factors make them less desirable for large scale industrial applications.
The disclosures in the art which cover aluminoxane compositions where R, as described above, can be selected from alkyl or, in some cases, aryl, all call for direct bonding of the R group to the aluminum atom. Examples of such disclosures include the following: U.S. Pat. Nos. 3,242,099 (R=C.sub.1 -C.sub.12 alkyl or aryl); 4,404,344 (R=C.sub.1 -C.sub.5 alkyl); 4,544,762 (R=C.sub.1 -C.sub.6 alkyl); 4,665,208 (R=C.sub.1 -C.sub.8 alkyl); 4,874,880 (R=hydrocarbyl such as C.sub.1 -C.sub.4 alkyl); 5,041,584 (R=C.sub.2 or higher alkyl); and European Patent Publication No. 324,856 (R=other than n-alkyl such as branched alkyl, cycloalkyl, or aryl).
Copending U.S. Ser. No. 853,466, filed Mar. 18, 1992, describes the manufacture of polymethylaluminoxane compositions of enhanced solution stability by reaction of the polymethylaluminoxane with certain organic compounds containing heteroatoms such as oxygen. Included as possible compounds are benzyl alcohol, nonyl phenol and butylated hydroxy toluene. The amount of such an organic compound is said to be no more than about 15 wt % of the polyaluminoxane, preferably up to about 10 wt %. Therefore, the resulting compositions, if an aryloxy-containing compound were selected, would contain a minor amount of aryloxy moieties.